[scheduler] Make any thread lock in TaskQueueImpl reentrable.

third_party/WebKit/Source/platform/scheduler/base/task_queue_impl.h

Index: third_party/WebKit/Source/platform/scheduler/base/task_queue_impl.h
diff --git a/third_party/WebKit/Source/platform/scheduler/base/task_queue_impl.h b/third_party/WebKit/Source/platform/scheduler/base/task_queue_impl.h
index 79503356b851cf354ffc12f40d93ef4b862e6fac..06907525f1aee3dfd8fdffafbfc42566f5705734 100644
--- a/third_party/WebKit/Source/platform/scheduler/base/task_queue_impl.h
+++ b/third_party/WebKit/Source/platform/scheduler/base/task_queue_impl.h
@@ -279,6 +279,26 @@ class BLINK_PLATFORM_EXPORT TaskQueueImpl final : public TaskQueue {
     base::trace_event::BlameContext* blame_context;  // Not owned.
     EnqueueOrder current_fence;
     base::TimeTicks scheduled_time_domain_wakeup;
+
+    // Number of times any thread lock was acquired from main thread to
+    // allow any thread lock be reentrable from main thread.
+    mutable size_t any_thread_lock_acquired_count;
+  };
+
+  // Helper class to make any_thread_lock reentrable from main thread.
+  // When |acquired_count| pointer is non-null, class uses is to
+  // allow for reentrability. When |acquired_count| is nullptr,
+  // this helper class behaves as a normal base::AutoLock.
+  class AnyThreadAutoLock {
+   public:
+    AnyThreadAutoLock(base::Lock& lock, size_t* acquired_count);
+    AnyThreadAutoLock(AnyThreadAutoLock&& auto_lock) = default;
+    ~AnyThreadAutoLock();
+
+   private:
+    base::Lock& lock_;
+    size_t* acquired_count_;
+    DISALLOW_COPY_AND_ASSIGN(AnyThreadAutoLock);
   };
 
   ~TaskQueueImpl() override;
@@ -330,6 +350,8 @@ class BLINK_PLATFORM_EXPORT TaskQueueImpl final : public TaskQueue {
   void OnQueueEnabledVoteChanged(bool enabled);
   void EnableOrDisableWithSelector(bool enable);
 
+  AnyThreadAutoLock AcquireAnyThreadLock() const;
+
   const base::PlatformThreadId thread_id_;
 
   mutable base::Lock any_thread_lock_;